This invention relates to a distance detector adaptable to small-sized cameras, particularly to a distance detector arranged to detect the distance from a camera to an object to be photographed by emitting a light from a light emission element directed at the object and receiving the light reflected by the object.
Conventional distance detectors of this type are provided with a plurality of light-receiving elements for receiving the reflected light and adapted to determine the range by identifying which one of the plurality of light-receiving elements receives the light emitted from a light emission element and reflected by the object to be photographed. For example, the distance detector as disclosed in Japanese Patent Laid-open No. 40663/79 is a zone focus type distance detector comprising a plurality of light-receiving elements each having conjugate relationship with a range and adapted to determine the range by identifying the particular light receiving-element which is in conjugate relationship with the range. The disadvantage of such conventional distance detector is that the distance detector is essentially incapable of continuously determining the distance due to the fact that it relies upon a plurality of light-receiving elements each in conjugate relationship with a distance. In order to increase the number of steps of range detection of the conventional distance detector, the number of light-receiving elements must be increased to determine the range in smaller steps and this, in turn, causes many problems. By way of example, the increase in the number of light-receiving elements causes problems such as the following: the output signal of each light-receiving element diminishes due to the reduction in the light receiving-area of the light-receiving element, a complicated input circuit is necessary due to the increase in the number of light-receiving elements, and a processing circuit is necessary to select the central element among plural elements which receive the reflected light or to obtain the average light intensity since the reflect light is received by a plurality of light-receiving elements.